Manufacture of viscose films, etc.



Patented Sept. 28, 1926.

UNITED STATE-S PATENT OFFICE.

J'AQUEB EDWIN BRANDENBEBGER, OI NEUILLY-SUB-SEINE, FRANCE.

MANUFACTURE OF VISCOSE FILMS, ETC.

11o Drawing. Original application flied June 19, 1923, Serial Kb. 646,478, and in France February 16,

1988. Divided and this application filed April 22, 1924. Serial No. 708,318;

The object of this invention is to provide aprocess of manufacturing, in a continuous manner, cellulose strips, films, and the like derived from aqueous solutions of sodium cellulose xanthate generally termed viscose.

The expression in a continuous manner, is intended to indicate that the operation is conducted in such a way that the liquid viscose, running uninterruptedly into a coagulating bath, is transformed without any interruption into -a finished product: strips, films, etc., consisting of regenerated cellulose obtained from sodium cellulose xanthat'e.

In certain former processes of making film, the xanthate solution was subjected to the coagulating action of a bath composed of an aqueous solution of ammonium sulphate or of other salts endowed with coagulating properties. The film so obtained was then treated by means of various successive baths for the purpose, first, of purifying it by means of an aqueous solution of sodium chloride, then of causing the xanthate to be transformed into cellulose under the action of a mineral acid, and lastly of washing it first with cold and next with hot water.

The present invention consists of a new process for manufacturing in a continuous manner threads, filaments, strips, films, tubes, etc., starting from viscose. Its essential difference from the one hitherto usedmention of which is to be found abovelies in this; that after the sodium cellulose xanthate has been coagulated in the first bath, its transformation into cellulose by means of a mineral acid follows immediately in the next bath, and the regenerated cellulose is then subjected to the action of certain baths, as will be explained later, for the purpose of purifying, dyeing, glycerinating, etc. The application is a division of my prior application, No. 646,478, filed June 19, 1923, which has been issued as Patent 1,548,864; dated Aug. 11, 1925.

In the following description, there will be discussed, for convenience, the application of the present process to the manufacture of films, which films are obtained by extruding viscose in the form of a sheet from a slotted hopper and allowing it to pass into the first coagulating bath; if it is desired to obtain threads, films, strips, tubes, etc., it would be necessary to use instead ofthe slotted hopper, a suitable device containing apertures through which the viscose is extruded, which apertures are adapted to make the kind of product desired.

In manufacturing film, the viscose or solution of sodium cellulose xanthate, as it issues from the slotted extruding hopper,

asses into a suitable coagulating bath. The 'lm so formed then travels, in a continuous manner, through a series of vats wherein it is supported by suitable guide rollers, the successive vats containing baths adapted for subsequent operations; but there is no occasion to emphasize the mechanical features of the apparatus. a

Onissuing from the first or coagulating bath, the film passes throu h a converting bath which causes the cellu ose xanthate to v be converted to cellulose; next the film is sub ected either to cold or to hot water washing and then to the action of a desulphuring bath; thereafter, the film is subjected to a second washing in either hot or cold water, at an rate hot at first, and finally is subecte to the action of a d eing bath. After this last operation, the lm is successively washed 1n running water, squeezed, put through a glycerine bath and ultimately dried either immediatel or later.

Reference will again be made to each one of the various aforementioned operations, specifying the operating method and the characterlstics for and of every one of them. Uoagulatz'on.0oagulation of the sodium cellulose xanthate is effected, as in former processes, by means of a bath containing, for instance, an aqueous solution of sulphate of ammonla; I can also utilize aqueous solutions-containing either a mixture of sulphate of ammonia and an acid, or a mixture of sulphate of ammonia and a base, or bisulphate of soda or sulphate of soda with an acid added thereto, or magnesium sulphate or zinc sulphate; furthermore I may utilize any two normal sulphates in combination.

When I use an acid coagulating bath or a bath containing bisulphates, I find that-in this coagulating bath the xanthate' immediately cellulose. The composition (proportion of constituents) of the coagulating bath actually used is determined by a number of factors, viz: the temperature of this bath, the degree to which the viscose has matured or ripened, the composition of the viscose,- the thickness ecomes partly transformed into desi of the film desired and the duration of contact of the viscose with the coagulating solution-which is determined by length of travel in the bath and machine speed.

There are, for instance, certain workmg conditions which hold good for all the following explanations and to whlch the example given will refer.

I will assume that the working s eed 1s 25 meters er minute, and that the lm to be obtained is to weigh from 25 to grams per square meter.

Under these conditions, and ut1l1z1ng 1n the first bath as a coagulatin solution am1 xture of sodium sulphate an sulphuncacid, the best results are obtained with thefollowin roportions, viz: 10 grams of sod1um sul p ate and 10 grams of sulphuric ac d per 100 cubic centimeters, the film remaining 1n the coagulating bath for about'35 seconds.

Trans arming bath.This bath, WhlCh 1s e to effect the transformation of the xant ate into cellulose and which is utilized immediately after coagulation and previous to all other operations, consists of an aqueous solution of a mineral acid such as, for instance, .hydrochloric acid, sulphuric acld Under the aforestated conditions (speed 25 meters per minute, film wei ht 25 to 30 grams per square meter) 0 results are obtained with a bath containing about 4%" grams of sulphuric acid in 100 cubic centimeters of water, about 35 seconds.

Washing.()nissuing from the transforming bath, the film is subjected to a cold or hot water washin to remove acid and salts. The film after acld treatment is o ue and white. If the washing is thorou t e film becomes somewhat transparent, ut it still contains a certain amount of sul hur which makes it somewhat opaque. T 's sulphur may be removed, however, by means of the desulphuring bath.

*DesuZphw'z'n g.The desulphuring bath consists either of ahot aqueous solution of sodium sulphide, the tem erature of which may be aslhi h as 100 or of a solution of caustic so a or of a solution of both or of an other body or substance endowed with a contact-duration of with esulphuring properties.

The composition of this bath depends on the same factors as those already mentioned. There may-be used, for instance, under the aforestated" conditions, a solution of about 0.4 gram or 0.5 gram of caustic soda for about 100 cubic centimeters of water, and the film may be allowed 15 seconds contact with the bath.

Washing.After desulphuration, the film is subjected to a washing with water in two vats. hot

This washing is preferably eifected high at any rate in the rst vat, and at as temperature as possible, even up 100 C. The desulghuring agent, which is carried over with t e film, is in fact of an alkaline nature and therefore ve diflicult to remove with cold water. The ot washing may, if desired, be followed by a cold water washing.

Dyei/ng. e film is next subjected to a dyeing treatment, which may be carried out by passing it through a vat or vats. The dyeing baths should have the same composition as those used for d eing cotton, artificial silk orany other ceilulosic fiber, in socalled continuous dyeing apparatus, the colors usually used for this purpose being the so-called direct colors. Dyei be effected at the same time as disulphuration by adding to the desulphuring bath coloring materials such as the so-called sulphur colors. It is also to be clearly understood that viscose may be used which has been colored previous to coagulation either by means of sulphur colorsor of any other coloring materials that will dissolve in viscose without decomposing.

Washing-After being dyed, the film is subjected to a washing 1n rapidly running water. This washing may be effected hot or cold, or even in two difierent baths, one hot and the other cold, with about 15 seconds stay in each bath.

may also Glycerine bath.After washing, the film mersion in the glycerine bath of about eight seconds, and the concentration of the glycerine bath is determined b the use for which the film is intended. T is concentration is greater when it is intended to make a more pliable film, and less when it is intended to make a less pliable film, but ordinarily the concentration is maintained so that the specific gravity of the glycerine solution is between 1.009 and 1.012.

After this treatment, the film may be squeezed and then placed in a suitable drying apparatus to dry.

It is to be understood that the process a plies equally to the case where inert su stances suc as barium sulphate, kaolin etc., have'been introduced into the viscose.

I claim as my invention:

1. A process for the continuous manufacture of cellulose films and the like, comprising the steps of coagulating an aqueous solution of sodium cellulose xanthate; passing the coagulated product through a transforming bath to convert it into. cellulose; washinglthe transformed product and passing it t rough a solution containin about 0.5 gram of caustic soda-per lcub1c centisulphate and 10 grams of sulphuric acid per 100 cubic centimeters of the mixture; maintaining the xanthate in motion in said mixture for about 35 seconds; tra-nsformin the coagulated product into cellulose; an desulphuring and dyeing the transformed product; and then glycerinating and drying the same.

3. A process for the continuous manufacture of cellulose films and the like, comprising the steps of coagulating an aqueous solution of sodium cellulose zanthate; passing the coagulated product through an aqueous mineral acid solution to transform it into cellulose; washing the transformed product with a solution containing about 0.5 gramof caustic soda per 100 cubic centimeters of Water to dcsulphur the same and dyeing it; and then, glycerinating and drying the product.

4. A process for the continuous manufacture of cellulose films and the like, comprising the steps of coagulating an aqueous solution of sodium cellulose xanthate; passing the coa lated product through an aque ous minera acid soltion to transform it into cellulose; Washing the transformed product with an aqueous solution of caustic soda containing about 0.5 gram of caustic soda per 100 cubic centimeters of water to desul phur it, and maintaining said product in such solution for about 15 seconds; dyeing the product; and then glycerinating and drying said product.

5. A process for the continuous manufacture of cellulose films and the like, c0mprising the steps of coa ulating a solution cf sodium cellulose Xantliate; transforming the coagulated product into cellulose; and then Washing the transformed product with an aqueous solution of caustic soda containing about 0.5 gram of caustic soda per 100 cubic centimeters of water to desulphur it.

6. A process for the continuous manufacture of cellulose films and the like, comprising the steps of coa ulating a solution of sodium cellulose xant ate; transforming the coagulated product into cellulose; Washing the transformed product with an aqueous solution of caustic soda containing about 0.5 gram of caustic soda per 100 cubic centimeters of water to desulphur it; dyeing the product; and then glycerinating and drying said product. a In testimony whereof I afiix my signature.

JAQUES EDWIN BRANDENBERGER. 

